Filters are NOT case-sensitive. So, entering "hello" will match "hello", "Hello", "HELLO", etc.
Filters with multiple criteria should put a single criterion per line.
Filters that look for "contains" look for for the text you enter between "word boundaries"... spaces, commas, @, angle brackets. Any non-letter characters, basically. So, to match any address at a domain (for instance, pobox.com):
To match a specific email address, just enter the email address. Quotes or angle brackets are not required.